Message-ID: <CAA93jw74dn1CvoCeMfRKz40Kj2hmDuDUcSFpAeLuPX5nkmzkdA@mail.gmail.com>
Date:   Mon, 25 Jan 2021 19:35:27 -0800
From:   Dave Taht <dave.taht@...il.com>
To:     Seth David Schoen <schoen@...alty.org>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        David Ahern <dsahern@...nel.org>, John Gilmore <gnu@...d.com>
Subject: Re: [PATCH net-next v2] selftests: add IPv4 unicast extensions tests

On Mon, Jan 25, 2021 at 3:44 PM Seth David Schoen <schoen@...alty.org> wrote:
>
> Add selftests for kernel behavior with regard to various classes of
> unallocated/reserved IPv4 addresses, checking whether or not these
> addresses can be assigned as unicast addresses on links and used in
> routing.
>
> Expect the current kernel behavior at the time of this patch. That is:
>
> * 0/8 and 240/4 may be used as unicast, with the exceptions of 0.0.0.0
>   and 255.255.255.255;
> * the lowest host in a subnet may only be used as a broadcast address;
> * 127/8 may not be used as unicast (the route_localnet option, which is
>   disabled by default, still leaves it treated slightly specially);
> * 224/4 may not be used as unicast.
> ---
>  tools/testing/selftests/net/Makefile          |   1 +
>  .../selftests/net/unicast_extensions.sh       | 228 ++++++++++++++++++
>  2 files changed, 229 insertions(+)
>  create mode 100755 tools/testing/selftests/net/unicast_extensions.sh
>
> diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile
> index fa5fa425d148..25f198bec0b2 100644
> --- a/tools/testing/selftests/net/Makefile
> +++ b/tools/testing/selftests/net/Makefile
> @@ -22,6 +22,7 @@ TEST_PROGS += devlink_port_split.py
>  TEST_PROGS += drop_monitor_tests.sh
>  TEST_PROGS += vrf_route_leaking.sh
>  TEST_PROGS += bareudp.sh
> +TEST_PROGS += unicast_extensions.sh
>  TEST_PROGS_EXTENDED := in_netns.sh
>  TEST_GEN_FILES =  socket nettest
>  TEST_GEN_FILES += psock_fanout psock_tpacket msg_zerocopy reuseport_addr_any
> diff --git a/tools/testing/selftests/net/unicast_extensions.sh b/tools/testing/selftests/net/unicast_extensions.sh
> new file mode 100755
> index 000000000000..936600082bba
> --- /dev/null
> +++ b/tools/testing/selftests/net/unicast_extensions.sh
> @@ -0,0 +1,228 @@
> +#!/bin/sh
> +# SPDX-License-Identifier: GPL-2.0
> +#
> +# By Seth Schoen (c) 2021, for the IPv4 Unicast Extensions Project
> +# Thanks to David Ahern for help and advice on nettest modifications.
> +#
> +# Self-tests for IPv4 address extensions: the kernel's ability to accept
> +# certain traditionally unused or unallocated IPv4 addresses. For each kind
> +# of address, we test for interface assignment, ping, TCP, and forwarding.
> +# Must be run as root (to manipulate network namespaces and virtual
> +# interfaces).
> +#
> +# Things we test for here:
> +#
> +# * Currently the kernel accepts addresses in 0/8 and 240/4 as valid.
> +#
> +# * Notwithstanding that, 0.0.0.0 and 255.255.255.255 cannot be assigned.
> +#
> +# * Currently the kernel DOES NOT accept unicast use of the lowest
> +#   host in an IPv4 subnet (e.g. 192.168.100.0/32 in 192.168.100.0/24).
> +#   This is treated as a second broadcast address, for compatibility
> +#   with 4.2BSD (!).
> +#
> +# * Currently the kernel DOES NOT accept unicast use of any of 127/8.
> +#
> +# * Currently the kernel DOES NOT accept unicast use of any of 224/4.
> +#
> +# These tests provide an easy way to flip the expected result of any
> +# of these behaviors for testing kernel patches that change them.
> +
> +# nettest can be run from PATH or from same directory as this selftest
> +if ! which nettest >/dev/null; then
> +       PATH=$PWD:$PATH
> +       if ! which nettest >/dev/null; then
> +               echo "'nettest' command not found; skipping tests"
> +               exit 0
> +       fi
> +fi
> +
> +result=0
> +
> +hide_output(){ exec 3>&1 4>&2 >/dev/null 2>/dev/null; }
> +show_output(){ exec >&3 2>&4; }
> +
> +show_result(){
> +       if [ $1 -eq 0 ]; then
> +               printf "TEST: %-60s  [ OK ]\n" "${2}"
> +       else
> +               printf "TEST: %-60s  [FAIL]\n" "${2}"
> +               result=1
> +       fi
> +}
> +
> +_do_segmenttest(){
> +       # Perform a simple set of link tests between a pair of
> +       # IP addresses on a shared (virtual) segment, using
> +       # ping and nettest.
> +       # foo --- bar
> +       # Arguments: ip_a ip_b prefix_length test_description
> +       #
> +       # Caller must set up foo-ns and bar-ns namespaces
> +       # containing linked veth devices foo and bar,
> +       # respectively.
> +
> +       ip -n foo-ns address add $1/$3 dev foo || return 1
> +       ip -n foo-ns link set foo up || return 1
> +       ip -n bar-ns address add $2/$3 dev bar || return 1
> +       ip -n bar-ns link set bar up || return 1
> +
> +       ip netns exec foo-ns timeout 2 ping -c 1 $2 || return 1
> +       ip netns exec bar-ns timeout 2 ping -c 1 $1 || return 1
> +
> +       nettest -B -N bar-ns -O foo-ns -r $1 || return 1
> +       nettest -B -N foo-ns -O bar-ns -r $2 || return 1
> +
> +       return 0
> +}
> +
> +_do_route_test(){
> +       # Perform a simple set of gateway tests.
> +       #
> +       # [foo] <---> [foo1]-[bar1] <---> [bar]   /prefix
> +       #  host          gateway          host
> +       #
> +       # Arguments: foo_ip foo1_ip bar1_ip bar_ip prefix_len test_description
> +       # Displays test result and returns success or failure.
> +
> +       # Caller must set up foo-ns, bar-ns, and router-ns
> +       # containing linked veth devices foo-foo1, bar1-bar
> +       # (foo in foo-ns, foo1 and bar1 in router-ns, and
> +       # bar in bar-ns).
> +
> +       ip -n foo-ns address add $1/$5 dev foo || return 1
> +       ip -n foo-ns link set foo up || return 1
> +       ip -n foo-ns route add default via $2 || return 1
> +       ip -n bar-ns address add $4/$5 dev bar || return 1
> +       ip -n bar-ns link set bar up || return 1
> +       ip -n bar-ns route add default via $3 || return 1
> +       ip -n router-ns address add $2/$5 dev foo1 || return 1
> +       ip -n router-ns link set foo1 up || return 1
> +       ip -n router-ns address add $3/$5 dev bar1 || return 1
> +       ip -n router-ns link set bar1 up || return 1
> +
> +       echo 1 | ip netns exec router-ns tee /proc/sys/net/ipv4/ip_forward
> +
> +       ip netns exec foo-ns timeout 2 ping -c 1 $2 || return 1
> +       ip netns exec foo-ns timeout 2 ping -c 1 $4 || return 1
> +       ip netns exec bar-ns timeout 2 ping -c 1 $3 || return 1
> +       ip netns exec bar-ns timeout 2 ping -c 1 $1 || return 1
> +
> +       nettest -B -N bar-ns -O foo-ns -r $1 || return 1
> +       nettest -B -N foo-ns -O bar-ns -r $4 || return 1
> +
> +       return 0
> +}
> +
> +segmenttest(){
> +       # Sets up veth link and tries to connect over it.
> +       # Arguments: ip_a ip_b prefix_len test_description
> +       hide_output
> +       ip netns add foo-ns
> +       ip netns add bar-ns
> +       ip link add foo netns foo-ns type veth peer name bar netns bar-ns
> +
> +       test_result=0
> +       _do_segmenttest "$@" || test_result=1
> +
> +       ip netns pids foo-ns | xargs -r kill -9
> +       ip netns pids bar-ns | xargs -r kill -9
> +       ip netns del foo-ns
> +       ip netns del bar-ns
> +       show_output
> +
> +       # inverted tests will expect failure instead of success
> +       [ -n "$expect_failure" ] && test_result=`expr 1 - $test_result`
> +
> +       show_result $test_result "$4"
> +}
> +
> +route_test(){
> +       # Sets up a simple gateway and tries to connect through it.
> +       # [foo] <---> [foo1]-[bar1] <---> [bar]   /prefix
> +       # Arguments: foo_ip foo1_ip bar1_ip bar_ip prefix_len test_description
> +       # Returns success or failure.
> +
> +       hide_output
> +       ip netns add foo-ns
> +       ip netns add bar-ns
> +       ip netns add router-ns
> +       ip link add foo netns foo-ns type veth peer name foo1 netns router-ns
> +       ip link add bar netns bar-ns type veth peer name bar1 netns router-ns
> +
> +       test_result=0
> +       _do_route_test "$@" || test_result=1
> +
> +       ip netns pids foo-ns | xargs -r kill -9
> +       ip netns pids bar-ns | xargs -r kill -9
> +       ip netns pids router-ns | xargs -r kill -9
> +       ip netns del foo-ns
> +       ip netns del bar-ns
> +       ip netns del router-ns
> +
> +       show_output
> +
> +       # inverted tests will expect failure instead of success
> +       [ -n "$expect_failure" ] && test_result=`expr 1 - $test_result`
> +       show_result $test_result "$6"
> +}
> +
> +echo "###########################################################################"
> +echo "Unicast address extensions tests (behavior of reserved IPv4 addresses)"
> +echo "###########################################################################"
> +#
> +# Test support for 240/4
> +segmenttest 240.1.2.1   240.1.2.4    24 "assign and ping within 240/4 (1 of 2) (is allowed)"
> +segmenttest 250.100.2.1 250.100.30.4 16 "assign and ping within 240/4 (2 of 2) (is allowed)"
> +#
> +# Test support for 0/8
> +segmenttest 0.1.2.17    0.1.2.23  24 "assign and ping within 0/8 (1 of 2) (is allowed)"
> +segmenttest 0.77.240.17 0.77.2.23 16 "assign and ping within 0/8 (2 of 2) (is allowed)"
> +#
> +# Even 255.255/16 is OK!
> +segmenttest 255.255.3.1 255.255.50.77 16 "assign and ping inside 255.255/16 (is allowed)"
> +#
> +# Or 255.255.255/24
> +segmenttest 255.255.255.1 255.255.255.254 24 "assign and ping inside 255.255.255/24 (is allowed)"
> +#
> +# Routing between different networks
> +route_test 240.5.6.7 240.5.6.1  255.1.2.1    255.1.2.3      24 "route between 240.5.6/24 and 255.1.2/24 (is allowed)"
> +route_test 0.200.6.7 0.200.38.1 245.99.101.1 245.99.200.111 16 "route between 0.200/16 and 245.99/16 (is allowed)"
> +#
> +# ==============================================
> +# ==== TESTS THAT CURRENTLY EXPECT FAILURE =====
> +# ==============================================
> +expect_failure=true
> +# It should still not be possible to use 0.0.0.0 or 255.255.255.255
> +# as a unicast address.  Thus, these tests expect failure.
> +segmenttest 0.0.1.5       0.0.0.0         16 "assigning 0.0.0.0 (is forbidden)"
> +segmenttest 255.255.255.1 255.255.255.255 16 "assigning 255.255.255.255 (is forbidden)"
> +#
> +# Test support for not having all of 127 be loopback
> +# Currently Linux does not allow this, so this should fail too
> +segmenttest 127.99.4.5 127.99.4.6 16 "assign and ping inside 127/8 (is forbidden)"
> +#
> +# Test support for lowest host
> +# Currently Linux does not allow this, so this should fail too
> +segmenttest 5.10.15.20 5.10.15.0 24 "assign and ping lowest host (is forbidden)"
> +#
> +# Routing using lowest host as a gateway/endpoint
> +# Currently Linux does not allow this, so this should fail too
> +route_test 192.168.42.1 192.168.42.0 9.8.7.6 9.8.7.0 24 "routing using lowest host (is forbidden)"
> +#
> +# Test support for unicast use of class D
> +# Currently Linux does not allow this, so this should fail too
> +segmenttest 225.1.2.3 225.1.2.200 24 "assign and ping class D address (is forbidden)"
> +#
> +# Routing using class D as a gateway
> +route_test 225.1.42.1 225.1.42.2 9.8.7.6 9.8.7.1 24 "routing using class D (is forbidden)"
> +#
> +# Routing using 127/8
> +# Currently Linux does not allow this, so this should fail too
> +route_test 127.99.2.3 127.99.2.4 200.1.2.3 200.1.2.4 24 "routing using 127/8 (is forbidden)"
> +#
> +unset expect_failure
> +# =====================================================
> +# ==== END OF TESTS THAT CURRENTLY EXPECT FAILURE =====
> +# =====================================================
> +exit ${result}
> --
> 2.25.1
>

Acked-By: Dave Taht <dave.taht@...il.com>

-- 
"For a successful technology, reality must take precedence over public
relations, for Mother Nature cannot be fooled" - Richard Feynman

dave@...t.net <Dave Täht> CTO, TekLibre, LLC Tel: 1-831-435-0729

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